Tuesday, March 27, 2007

H5N1 Watch -- Experts Are On the Job

This summary from the NY Times is not easy reading for laymen. Too many references to the particulars of biochemistry and such. But I find scanning it to be reassuring. Despite the hype smart people all over the world are keeping watch on the spread of this deadly virus, waiting to react swiftly when a mutation occurs jumping the species barrier to humans, triggering a human-to-human strain. When that happens, the much talked about pandemic will be underway.

...even though the human death toll from H5N1 is still below 200, scientists around the world are racing to study the ways in which it might mutate to spread easily among humans.

The 1918 Spanish flu, they argue, was not even noticed until it had killed thousands. It might have been gathering virulence for years, hidden in the background of seasonal flu deaths.

Today’s H5N1 flu is probably changing more slowly, because health officials have been vigilant about attacking clusters of cases, which presumably wipes out the most dangerous strains. Whenever several human cases appear, even in remote villages in Indonesia or Egypt, local officials and World Health Organization teams move in to kill all the local poultry and dose all the humans with antiviral drugs — the so-called Tamiflu blanket strategy.
...flus mutate incessantly wherever they move, and in viral samples from Asia, the Middle East and Africa, many individual changes that look potentially dangerous have been spotted.

In May 2005, for example, the virus in China escaped in migratory birds going north and traveled across Russia, Europe and Africa. It became known as the Qinghai strain after the lake in Northern China where thousands of ducks and geese were found dead. (The older strain in Southern China and Southeast Asia is sometimes called the Fujian strain.)

The Qinghai strain has a mutation known as PB2 E627K. (The abbreviation can be read this way: at position No. 627 on polymerase basic protein 2, the amino acid called glutamic acid, abbreviated by scientists as E, has been replaced by lysine, known as K.)

The change helps the virus grow at the temperatures found in human noses, which are cooler than the insides of birds’ intestines.

It is “characteristic of a gene that’s been in mammals,” said Dr. Robert G. Webster, a virologist at St. Jude Children’s Research Hospital in Memphis. “It says to me that it was in a mammalian species in China, and got back into ducks. But what species? We don’t know.”

The Qinghai strain has now reached about 50 countries.

Thanks H5N1 Blog for the link.

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